what type of ram are you running ? 2100 DDR or something faster ?, in the event that your ram is 2700 or 3200 you would have mis matched speeds for the ram and the bus. If thats the case try underclocking the ram so that it matchs the 133 mhz fsb.
hope that helps.
As for the card, if it's a new one what was the old ? Nvidia, and if so did you pull all the old drivers out first with drivercleaner or did you do a fresh install. A bit more information on your system would help and what you were running the last time it was stable.
Gary
....................
<font color=red>AMD 2700 XP<font color=red>
<font color=red>Gecube 9800 pro Extreme<font color=red>
<font color=blue>ASUS A7N8X deluxe<font color=blue>
<font color=blue>1024 meg Dual Channel DDR 3200<font color=blue>
....................